Instance DB

BoSChoW · May 2, 2006

Hey y'all,
i am transfering a lot of parameters from the OP7 to the PLC CPU313C and i want that this parameters are stored in the PLC, so that i can use them later even if i switch the PLC off. Are the instance DB designed for this?

manmeetvirdi · May 3, 2006

hi there

You can communicata between PLC and OP with the help of Data Blocks.All the data in DB are stored in Micro Memory Card, so it is retentive.
You can also use system bits like "M", to communicate but as you asked its not retentive.
Instanace data block are FB specific. So only that particular FB can use it.

STL??? · May 3, 2006

you can define how much "M" memory,timers,counters are retentive in the CPU properties of your Hardware.

RMA · May 4, 2006

Instanace data block are FB specific. So only that particular FB can use it.

This is not quite right. Instance DBs are just the same as any other DB and can be accessed from anywhere in the program. If you're just reading data from then, then you can use them without any second thoughts. If you want to start writing to them from somewhere other than the parent FB, however, you better be really sure you know what you're doing!

Arun · May 4, 2006

I have Sufina808 machine when i transfer program to machine sufina says that you have to create instsant DBs to some given DB then and then machine runs OK Why it is so?

BoSChoW · May 24, 2006

I have finally checked the CPU properties retentive memory, but i dont know how to assign which M bites are retentive, how do i do that since the retentive memory area are not changable...

STL??? · May 24, 2006

Open up the CPU Properties in the Hardware config(right click on the CPU~Slot2) and the values wont be read only.

Retentive Memory tab
Number of memory bytes starting at MB0

BoSChoW · May 24, 2006

So now i have to check how many memory bytes can be stored in retentive memory for my PLC. And then i change the number of bytes, and this is it ?

STL??? · May 25, 2006

Define how many bytes you wish to be retentive, Save + Compile and download to your CPU.

Just be careful not to assign to many bytes and end up outside the boundary supported by your CPU, From memory for example a 64KB 315DP max M byte is 0-255.7

Hope this helps

BoSChoW · May 26, 2006

Thanks again man, you saved my day again. Regards.

Fox · May 28, 2006

If you need more retentive memory than the available M bits you should use a DB instead. Then you folow same procedure to define the amount of bytes you need retentive in that DB (theoretically you can use 64Kbytes in each DB).

BoSChoW · May 29, 2006

Hi,
i am useing retentive memory to store the parameter that i transfer from the OP7 to the PLC. When i used the DB, and typed the number on the OP7 the numbner switched from 5 back to 0, and so i tryed to use memory bits instead and its working. I would like to make the program work with the DB but i dont know what i did wrong, since the same program works if i use M bits... the only difference is in the symbol where i defined M bit by M bit "input1 - M0.0 and timer1 - MW2" all the parameters...while useing DB i defined just the data block and its symbolic name "DB5 - inputs" ... i will try and make
the same for the data block as i did for the M bits "inputs1 - DB.DBX0.0"...maybe is this the cause...

Thanks man, regards.

Fox · May 31, 2006

Hi,

If you use DB.DBX0.0 it won't work. You must use DB5.DBX0.0

Was this your program mistake or you just forgot to write the DB number here?

BoSChoW · May 31, 2006

I forgot to write the DB number here. My mistake was that i didnt specify each bit of DB in the symbolic table, i just put in the whole DB...i guess this was my mistake....

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